John W. Prather

Spatial and temporal activity patterns of the brood parasitic brown-headed cowbird at an urban/wildland interface

We examined the impact of the urban environment on the spatial and temporal activity of brood parasitic Brown-headed Cowbirds (Molothrus ater) in Boulder County, CO, USA. We found that cowbirds used the urban areas for foraging and roosting and traveled into the 3240 ha wildland preserve of ponderosa pine in the mornings to parasitize songbird hosts. Cowbird abundance decreased with distance from the urban/wildland boundary, and Plumbeous Vireo (Vireo plumbeus) nests closer to the urban/wildland boundary were more likely to be parasitized by cowbirds than those farther away. A linear regression accurately predicted the relative abundance of cowbirds based on parameters of distance from residential areas, and distance from roads and trails within the wildland preserve. For species of concern that are known cowbird hosts, creating larger preserves, reducing residential encroachment, and reducing preserve perforation by roads and trails might alleviate high frequencies of parasitism for a portion of the host population. However, even large preserves, such as found in Boulder, CO, USA cannot insulate all focal nesting species from the urban effect of increased brood parasitism. Efforts to reduce food resources and cover for cowbirds in the urban areas might prove to ameliorate host reproductive success close to the urban/wildland boundary through decreases in cowbird abundance.

Seasonal Use and Selection of Caves by the Eastern Pipistrelle Bat (Pipistrellus subflavus)

Abstract The eastern pipistrelle (Pipistrellus subflavus) is considered one of the most common and widely distributed species of bats in eastern North America, but little published information exists on its natural history. During surveys of numerous small caves in northwest Arkansas, we documented use by eastern pipistrelles and recorded ambient temperature readings in all caves and at roost and hibernation sites for individual bats. Using presence/absence data and a GIS system, we examined association of pipistrelle occurrence based upon landscape-level variables and cave structure. Hibernating eastern pipistrelles showed a significant preference for cave openings with east-facing aspects and significantly avoided caves on steep slopes during winter. These patterns appear to be due to the influence of cave ambient temperature. Significantly more eastern pipistrelles were found in caves with a wide range of temperature regimes within a season, but with little temperature variation between seasons. In our study site caves with east-facing aspects and on shallow slopes were significantly larger than those on the steep west-facing slopes. Larger caves have a greater buffer capacity from weather conditions, offering a wider range of temperature profiles within a season but varying little between seasons for consistent use by hibernating eastern pipistrelle bats.

EFFECTS OF EXPERIMENTAL EGG COMPOSITION ON REJECTION BY VILLAGE WEAVERS (PLOCEUS CUCULLATUS)

Abstract We experimentally parasitized nests of the Village Weaver (Ploceus cucullatus) in Hispaniola using real and artificial eggs made from wood and modeling clay. Artificial eggs were similar in size and shape to real weaver eggs and were coated with acrylic paint and glazed. Real eggs were actual weaver eggs taken from Village Weaver nests. Experimental parasitic eggs (1) mimicked natural weaver eggs, (2) differed in color only, (3) differed in spotting only, or (4) mimicked Shiny Cowbird (Molothrus bonariensis) egg color and spotting pattern. Parasitized nests were checked after 2–6 days. Real eggs were ejected from weaver nests with increasing frequency as they became less similar to the eggs in the nest with cowbirds eggs having the highest rejection (81%). However, for artificial egg types there were no significant within-composition differences in patterns of rejection. Clay eggs were usually ejected from the nests, whereas nests containing wood eggs often ended empty, or with only the artificial egg remaining in the nest. These patterns may reflect the differential ability of weavers to recognize and remove foreign eggs of different compositions from their nests. Researchers undertaking egg-rejection experiments should use real eggs either in addition or in place of artificial eggs to assess the cost of rejection and the coevolutionary relationships between parasite and host.

Seasonal Use and Selection of Caves by Plethodontid Salamanders in a Karst Area of Arkansas

Abstract From December 1998 through May 2000, seasonal use and selection of caves by salamanders were documented in 93 small caves in Crawford County, Arkansas. Caves were surveyed seasonally between winter 1998–1999 and spring 2000, and the numbers and species of all salamanders present were documented. Cave ambient temperature and relative humidity were recorded. Also, each cave entrance was georeferenced using GPS (Global Positioning System) and landscape-level variables around each entrance were quantified using ArcView GIS (Geographic Information System) data layers. Using salamander and ArcView data, relations between salamander occurrence based upon landscape-level variables (dominant overstory vegetation, geology, slope, aspect, solar radiation and distance to perennial stream) and cave characteristics (ambient temperature, relative humidity, cave length and entrance size) were examined. Six species of salamanders were found during the survey. Eurycea lucifuga (cave salamander), Plethodon albagula (western slimy salamander) and P. angusticlavius (Ozark salamander) were commonly observed. Eurycea lucifuga salamanders were active in caves during spring, summer and autumn. Plethodon albagula were most frequently encountered during the summer and P. angusticlavius were most frequently encountered during spring surveys. Few salamanders of any species were detected during winter surveys. The use of caves by the various species of salamanders was influenced by the landscape-level variables and cave characteristics. However, cave ambient temperature and relative humidity appear to have the most influences of salamander use of caves. Both E. lucifuga and P. albagula were significantly more likely to be found in caves with cooler temperatures in summer and higher relative humidities in autumn. In addition to these factors, the probability of finding E. lucifuga significantly decreased with increasing distance to permanent streams, whereas P. albagula was significantly more likely to be found in caves with south and west facing aspects, especially during summer and autumn surveys. There were no significant patterns for P. angusticlavius use of caves. Seasonal and spatial patterns of cave use by salamanders were primarily influenced by environmental (temperature and relative humidity) factors and the ecological requirements of the salamanders.

Use of Small Caves by Anurans during a Drought Period in the Arkansas Ozarks

Evolution and biogeography of the genus Tarentola (Sauria: Gekkonidae) in the Canary Islands, inferred from mitochondrial DNA sequences. J. Evol. Biol. 11:481-494. POSADA, D., AND K. A. CRANDALL. 1998. Modeltest: testing the model of DNA substitution. Bioinformatics 14:817-818. POWELL, R., R. I. CROMBIE, AND H. E. A. Boos. 1998. Hemidactylus mabouia. Cat. Am. Amphib. Reptiles 674.1-674.11. RODRIGUEZ, F, J. E OLIVER, A. MARIN, AND J. R. MEDINA. 1990. The general stochastic model of nucletide substitutions. J. Theor. Biol. 142:485-501 SCHLEICH, H. H. 1987. Herpetofauna Caboverdiana. Spixiana 12:1-75 STRIMMER, K., AND A. VON HAESLER. 1996. Quartet puzzling: a quartet maximum-likelihood method for reconstructing tree topologies. Mol. Biol. Evol. 13:964-969. SWOFFORD, D. L. 2000. PAUP*: Phylogenetic Analysis Using Parsimony (and Other Methods). 4.0.b3a. Sinauer Associates, Sunderland, MA. THOMPSON, J. D., D. G. HIGGINS, AND T. J. GIBSON. 1994. Clustal W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position specific gap penalties and weight matrix choice. Nucl. Acid. Res. 22: 4673-4680. YANG, Z. 1994. Maximum likelihood phylogenetic estimation from DNA sequences with variable rates over sites: approximate methods. J. Mol. Evol. 39: 306-314.

Use of Small Caves by Ozark Big-eared Bats(Corynorhinus townsendii ingens) in Arkansas

Abstract The Ozark big-eared bat (Corynorhinus townsendii ingens) is an endangered subspecies currently known only from small populations in Arkansas and Oklahoma. Between October 1998 and May 2000 we surveyed 93 small caves in northwestern Arkansas six times. During these surveys we encountered Ozark big-eared bats in 8–10 caves every season. During surveys in spring, summer and autumn, we encountered mainly lone individuals, while up to seven individuals were encountered together during winter surveys. Winter encounters were mainly in limestone caves, particularly those with vertical or near vertical sinkhole entrances, whereas caves with more varied characteristics were used in other seasons. Temperature may also have been a factor in choice of caves, with colder caves being preferred, especially in winter. Our data indicate that Ozark big-eared bats use many small caves in the study area. These caves should be protected, and other groups of small caves in the Ozarks should be surveyed for Ozark big-eared bats.

Breeding Biology of Red-winged Blackbirds in South Florida

Abstract We studied the breeding biology of two Agelaius phoeniceus (Red-winged Blackbird) populations in south Florida. Red-winged Blackbirds in our study bred at low relative abundance in a wide variety of habitats, were rarely socially polygynous, and were highly aggressive toward intruders. The breeding season extended from March through August and coincided with the rainy season. Nesting periods were similar to those reported for other subspecies of Red-winged Blackbirds, but clutch sizes were small, with 2- and 3-egg clutches predominating. Nesting success varied from 28% on Sanibel Island to 63% on the Florida Keys. Both populations accepted a majority of artificial eggs into their nests, although cowbird parasitism has been rarely reported in south Florida.